Integrated circuits are manufactured by a highly complex manufacturing process. Various manufacturing process faults can result in the deposition of microscopic elements on the integrated circuits. Solving these various manufacturing faults can be assisted by determining the materials from which these microscopic elements are made of.
Various material analysis methods focus on a charged particle beam (such as an electron beam or an ion beam) or an X-ray beam onto a microscopic element of interest. This charged particle beam typically charges the microscopic element and additionally or alternatively, specimen portions that are proximate to that microscopic element. This charging can deflect the charged particle beam from the microscopic element. Thus, after a certain period the charged particle beam can totally miss the element of interest and the material analysis will not reflect the materials from which the microscopic element is made of.
FIG. 1 illustrates microscopic element 8 and a displacement of a charged particle beam over time. At a beginning of the illumination, a charged particle beam (illustrated by dashed line 12) is directed towards microscopic element 8. The charged particle beam charges a portion 20 of specimen (illustrated by a horizontal dashed line below microscopic element 8). The charged portion 20 generates an electrical field that displaces the charged particle beam. After a while the charged particle beam (illustrated by dashed line 14) is directed towards the surrounding of the microscopic element and does not interact with microscopic element 8.
FIG. 2 illustrates the microscopic element and various areas that are scanned during different points in time, due to the displacement of the charge particle beam. The displacement results e.g. from the charging of the specimen (or a portion thereof). When the scanning starts microscopic element 8 is located at the center of area 30. After a while, the scanning electron microscope is directed towards another area 32 and microscopic element 8 is not located at the center to this area. After additional time microscopic element 8 is completely outside area 36 that is scanned by the charged electron beam. It is noted that this displacement, which in this example resulted from charging effects, is not the result of a deliberate alteration of a parameter of charged particle beam optics.
FIG. 3 illustrates an example of the displacement (drift) of an electron beam measured in a blanket silicon glass wafer that was tilted at about forty five degrees in relation to a scanning electron microscope column. The drift rate along the Y axis was about 1.4 nanometers per second while the drift rate along the X axis was lower. It is expected that if a small microscopic element area is to be scanned by electron beam (for example, electron beam spot placed within microscopic element of 30 nm×30 nm) for material analysis, then after about 10 seconds the microscopic element will be out of the electron beam spot. It is further expected that the drift rate will be much faster when scanning a more easily charging specimen such as those made of low K dielectric materials.
There is a growing need to provide a system and a method for material analysis on small microscopic elements (for example, about 50 nm and less).